Along with the development of thin film transistor liquid crystal display (TFT-LCD) technology, more and more new technologies have been presented and applied. Among them, the TFT-LCD in an advanced super dimension switch (AD-SDS, ADS for short) mode has attracted more and more attention due to its features such as low power consumption and wide view angle.
For the ADS technology, it mainly refers to the formation of a multi-dimensional electric field through electric fields generated at edges of slit electrodes in an identical plane and an electric field generated between a slit electrode layer and a plate electrode layer, so as to rotate all the orientational liquid crystal molecules between the slit electrodes and right above the electrodes in a liquid crystal cell, thereby to improve the working efficiency of the liquid crystal molecules and increase the light transmittance. A TFT-LCD product using the ADS technology can provide excellent image quality, and meanwhile has such advantages as a high resolution, high light transmittance, a wide view angle, a high aperture ratio, low chromatic aberration, and no push Mura.
As compared to a TFT with an active layer made of a-Si in the prior art, the TFT with an active layer made of a metal oxide has such features as a high migration rate, a low manufacturing temperature, well uniformity, being transparent to visible light, and a low threshold voltage. Hence, it may be used to achieve a high aperture ratio and low power consumption, and will have great potential in future.
Hence, a display substrate with the advantages of both the ADS technology and the metal oxide TFT will have greater potential in future. However, the metal oxide is susceptible to H2 and H2O. In order to prevent the metal oxide from being adversely affected by an etchant used in a subsequent wet etching step, it is required to add a barrier layer on a surface of the metal oxide for protection. Usually, the barrier layer is required to be subjected to a single mask exposure process separately, so as to form via-holes, through which a source/drain electrode of the TFT connects with the metal oxide. Such a structure results in an increase in the production cost of a mask plate as well as a complex process.
For the ADS-type TFT-LCD with the active layer made of the metal oxide, seven patterning processes are required in the prior art, and each patterning process includes such steps as film-forming, exposing, developing, etching and peeling off. Too many patterning processes will directly result in an increase in the production cost of a display device. Hence, there is an urgent need to further reduce the number of the patterning processes.